GPUImage的基础应用（一）：图片添加滤镜

闲来没事儿，就自己研究了一下GPUImage的用法。之前一直听朋友说到这个东西，就知道功能很强大，本人项目中确实没用到过，所以暂未接触。

框架导入

我用的cocoaPods，用法非常简单：
新建Podfile文件
cd 工程目录
vim Podfile
然后在Podfile文件中编辑：

platform:ios,'9.0'

target "LGJDemo" do
    
pod 'GPUImage'

end

执行pod install 等待完成就OK了。

用法也是非常的简单，大致过程如下：
1、拿到一张图片
2、创建过滤器对象，并设置需要渲染的区域
3、根据图片获取数据源，并添加上滤镜，开始渲染
4、获取渲染后的图片，显示出来

图片手动添加滤镜

其具体实现代码如下：

//拿到图片
    NSString *path = [[NSBundle mainBundle]pathForResource:@"DSC_4156" ofType:@"jpg"];
    UIImage *inputImage = [UIImage imageWithContentsOfFile:path];

//装饰图案滤镜
    GPUImageVignetteFilter *filter = [[GPUImageVignetteFilter alloc]init];

//设置需要渲染的区域
    [filter forceProcessingAtSize:inputImage.size];

//usingNextFrameForImageCapture代表着输出的结果会被用于获取图像
    [filter useNextFrameForImageCapture];

    //获取数据源
    GPUImagePicture *imageSource = [[GPUImagePicture alloc]initWithImage:inputImage];
    
    //添加上滤镜
    [imageSource addTarget:filter];
    
    //开始渲染
    [imageSource processImage];
    
    //获取渲染后的图片
    UIImage *new = [filter imageFromCurrentFramebuffer];
    
    //显示出来
    UIImageView *imageView = [[UIImageView alloc]initWithImage:new];
    imageView.frame = CGRectMake(50, 50, new.size.width, new.size.height);
    [self.view addSubview:imageView];

运行以上代码就可以看到不一样的效果了。下面是添加特效之前和之后的照片对比。

原图 GPUImageVignetteFilter

图片自动添加滤镜

-(void)imageAotuAddFilter{//自动添加滤镜
    NSString *path = [[NSBundle mainBundle]pathForResource:@"DSC_4156" ofType:@"jpg"];
    UIImage *image = [UIImage imageWithContentsOfFile:path];
    
    GPUImageSepiaFilter *sepiaFilter = [[GPUImageSepiaFilter alloc]init];
    
    UIImage *currentImage = [sepiaFilter imageByFilteringImage:image];
    
    UIImageView *imageView = [[UIImageView alloc]initWithFrame:self.view.frame];
    imageView.image = currentImage;
    [self.view addSubview:imageView];
}

拍照添加滤镜

-(void)takingPicturesAddFilter{//拍照滤镜
    GPUImageStillCamera *camera = [[GPUImageStillCamera alloc]init];
    self.stillCamera = camera;
    camera.outputImageOrientation = UIInterfaceOrientationPortrait;
    
    GPUImageHazeFilter *hueFilter = [[GPUImageHazeFilter alloc]init];
    [camera addTarget:hueFilter];
    
    GPUImageView *_imageView = [[GPUImageView alloc]initWithFrame:CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height)];
    [self.view addSubview:_imageView];
    
    [hueFilter addTarget:_imageView];
    
    [camera startCameraCapture];
}

其实咱们只是运用了GPUImage所提供的众多过滤器中的一种，GPUImage提供的过滤器很多，下面是GPUImage所包含的类。至于添加过滤器之后的照片特效，我们可以一一尝试。

// Base classes
#import "GPUImageContext.h"
#import "GPUImageOutput.h"
#import "GPUImageView.h"
#import "GPUImageVideoCamera.h"
#import "GPUImageStillCamera.h"
#import "GPUImageMovie.h"
#import "GPUImagePicture.h"
#import "GPUImageRawDataInput.h"
#import "GPUImageRawDataOutput.h"
#import "GPUImageMovieWriter.h"
#import "GPUImageFilterPipeline.h"
#import "GPUImageTextureOutput.h"
#import "GPUImageFilterGroup.h"
#import "GPUImageTextureInput.h"
#import "GPUImageUIElement.h"
#import "GPUImageBuffer.h"
#import "GPUImageFramebuffer.h"
#import "GPUImageFramebufferCache.h"

// Filters
#import "GPUImageFilter.h"
#import "GPUImageTwoInputFilter.h"
#import "GPUImagePixellateFilter.h"
#import "GPUImagePixellatePositionFilter.h"
#import "GPUImageSepiaFilter.h"
#import "GPUImageColorInvertFilter.h"
#import "GPUImageSaturationFilter.h"
#import "GPUImageContrastFilter.h"
#import "GPUImageExposureFilter.h"
#import "GPUImageBrightnessFilter.h"
#import "GPUImageLevelsFilter.h"
#import "GPUImageSharpenFilter.h"
#import "GPUImageGammaFilter.h"
#import "GPUImageSobelEdgeDetectionFilter.h"
#import "GPUImageSketchFilter.h"
#import "GPUImageToonFilter.h"
#import "GPUImageSmoothToonFilter.h"
#import "GPUImageMultiplyBlendFilter.h"
#import "GPUImageDissolveBlendFilter.h"
#import "GPUImageKuwaharaFilter.h"
#import "GPUImageKuwaharaRadius3Filter.h"
#import "GPUImageVignetteFilter.h"
#import "GPUImageGaussianBlurFilter.h"
#import "GPUImageGaussianBlurPositionFilter.h"
#import "GPUImageGaussianSelectiveBlurFilter.h"
#import "GPUImageOverlayBlendFilter.h"
#import "GPUImageDarkenBlendFilter.h"
#import "GPUImageLightenBlendFilter.h"
#import "GPUImageSwirlFilter.h"
#import "GPUImageSourceOverBlendFilter.h"
#import "GPUImageColorBurnBlendFilter.h"
#import "GPUImageColorDodgeBlendFilter.h"
#import "GPUImageScreenBlendFilter.h"
#import "GPUImageExclusionBlendFilter.h"
#import "GPUImageDifferenceBlendFilter.h"
#import "GPUImageSubtractBlendFilter.h"
#import "GPUImageHardLightBlendFilter.h"
#import "GPUImageSoftLightBlendFilter.h"
#import "GPUImageColorBlendFilter.h"
#import "GPUImageHueBlendFilter.h"
#import "GPUImageSaturationBlendFilter.h"
#import "GPUImageLuminosityBlendFilter.h"
#import "GPUImageCropFilter.h"
#import "GPUImageGrayscaleFilter.h"
#import "GPUImageTransformFilter.h"
#import "GPUImageChromaKeyBlendFilter.h"
#import "GPUImageHazeFilter.h"
#import "GPUImageLuminanceThresholdFilter.h"
#import "GPUImagePosterizeFilter.h"
#import "GPUImageBoxBlurFilter.h"
#import "GPUImageAdaptiveThresholdFilter.h"
#import "GPUImageUnsharpMaskFilter.h"
#import "GPUImageBulgeDistortionFilter.h"
#import "GPUImagePinchDistortionFilter.h"
#import "GPUImageCrosshatchFilter.h"
#import "GPUImageCGAColorspaceFilter.h"
#import "GPUImagePolarPixellateFilter.h"
#import "GPUImageStretchDistortionFilter.h"
#import "GPUImagePerlinNoiseFilter.h"
#import "GPUImageJFAVoronoiFilter.h"
#import "GPUImageVoronoiConsumerFilter.h"
#import "GPUImageMosaicFilter.h"
#import "GPUImageTiltShiftFilter.h"
#import "GPUImage3x3ConvolutionFilter.h"
#import "GPUImageEmbossFilter.h"
#import "GPUImageCannyEdgeDetectionFilter.h"
#import "GPUImageThresholdEdgeDetectionFilter.h"
#import "GPUImageMaskFilter.h"
#import "GPUImageHistogramFilter.h"
#import "GPUImageHistogramGenerator.h"
#import "GPUImageHistogramEqualizationFilter.h"
#import "GPUImagePrewittEdgeDetectionFilter.h"
#import "GPUImageXYDerivativeFilter.h"
#import "GPUImageHarrisCornerDetectionFilter.h"
#import "GPUImageAlphaBlendFilter.h"
#import "GPUImageNormalBlendFilter.h"
#import "GPUImageNonMaximumSuppressionFilter.h"
#import "GPUImageRGBFilter.h"
#import "GPUImageMedianFilter.h"
#import "GPUImageBilateralFilter.h"
#import "GPUImageCrosshairGenerator.h"
#import "GPUImageToneCurveFilter.h"
#import "GPUImageNobleCornerDetectionFilter.h"
#import "GPUImageShiTomasiFeatureDetectionFilter.h"
#import "GPUImageErosionFilter.h"
#import "GPUImageRGBErosionFilter.h"
#import "GPUImageDilationFilter.h"
#import "GPUImageRGBDilationFilter.h"
#import "GPUImageOpeningFilter.h"
#import "GPUImageRGBOpeningFilter.h"
#import "GPUImageClosingFilter.h"
#import "GPUImageRGBClosingFilter.h"
#import "GPUImageColorPackingFilter.h"
#import "GPUImageSphereRefractionFilter.h"
#import "GPUImageMonochromeFilter.h"
#import "GPUImageOpacityFilter.h"
#import "GPUImageHighlightShadowFilter.h"
#import "GPUImageFalseColorFilter.h"
#import "GPUImageHSBFilter.h"
#import "GPUImageHueFilter.h"
#import "GPUImageGlassSphereFilter.h"
#import "GPUImageLookupFilter.h"
#import "GPUImageAmatorkaFilter.h"
#import "GPUImageMissEtikateFilter.h"
#import "GPUImageSoftEleganceFilter.h"
#import "GPUImageAddBlendFilter.h"
#import "GPUImageDivideBlendFilter.h"
#import "GPUImagePolkaDotFilter.h"
#import "GPUImageLocalBinaryPatternFilter.h"
#import "GPUImageLanczosResamplingFilter.h"
#import "GPUImageAverageColor.h"
#import "GPUImageSolidColorGenerator.h"
#import "GPUImageLuminosity.h"
#import "GPUImageAverageLuminanceThresholdFilter.h"
#import "GPUImageWhiteBalanceFilter.h"
#import "GPUImageChromaKeyFilter.h"
#import "GPUImageLowPassFilter.h"
#import "GPUImageHighPassFilter.h"
#import "GPUImageMotionDetector.h"
#import "GPUImageHalftoneFilter.h"
#import "GPUImageThresholdedNonMaximumSuppressionFilter.h"
#import "GPUImageHoughTransformLineDetector.h"
#import "GPUImageParallelCoordinateLineTransformFilter.h"
#import "GPUImageThresholdSketchFilter.h"
#import "GPUImageLineGenerator.h"
#import "GPUImageLinearBurnBlendFilter.h"
#import "GPUImageGaussianBlurPositionFilter.h"
#import "GPUImagePixellatePositionFilter.h"
#import "GPUImageTwoInputCrossTextureSamplingFilter.h"
#import "GPUImagePoissonBlendFilter.h"
#import "GPUImageMotionBlurFilter.h"
#import "GPUImageZoomBlurFilter.h"
#import "GPUImageLaplacianFilter.h"
#import "GPUImageiOSBlurFilter.h"
#import "GPUImageLuminanceRangeFilter.h"
#import "GPUImageDirectionalNonMaximumSuppressionFilter.h"
#import "GPUImageDirectionalSobelEdgeDetectionFilter.h"
#import "GPUImageSingleComponentGaussianBlurFilter.h"
#import "GPUImageThreeInputFilter.h"
#import "GPUImageWeakPixelInclusionFilter.h"